2. According to origin, i. e., whether they arise from blood clot or other causes.
3. According to contents, whether they contain clear fluid, altered clot, or brain substance.
Cysts of this character are to be differentiated from the cephaloceles already considered because there is about most of them the element of traumatism, although this may have been intra-uterine or produced during parturition. Those which are associated with premature synostosis and microcephaly, with hydrocephalus, with marked deformity, or situated below the external occipital protuberance, are generally considered inoperable, while those considered operable consist of limited protrusions without any of the above defects. This practically excludes the greater proportion of these cases from operation, which is always dangerous. Nevertheless if success is to be achieved the risks should be taken. Osteoplastic methods of closing cranial openings may be perhaps of value in rare cases, although in the young the skull is too thin to furnish an external table which can of itself be detached. In inoperable cysts of this kind, with a tendency to increase, while the rest of the brain lags behind in the rate of growth, the edges of the opening become everted, and operation is thus made more difficult and less desirable.
Treatment.
—Treatment should, first of all, be protective, by a shield of some device held in place by a suitable bandage or dressing. Compression, with or without puncture, has given at times satisfactory results, but not much should be expected from any method or combination. Most of the cases are such that extirpation would seem applicable, but the impossibility of absolute asepsis in young infants and the liability to fatal shock preclude many of these attempts. In some instances ligature of a meningocele has been successfully applied. Operation may be attempted in young children in selected cases. Plastic operations may be resorted to, or plastic maneuvers combined with extirpation. It may be possible by the insertion of a celluloid plate to atone for a small defect in the skull after extirpation of a tumor of this kind. I have successfully practised this method in spina bifida.
HYDROCEPHALUS.
This term is applied to abnormal collections of cerebrospinal fluid within the cranial cavity. We speak of—
A. Hydrocephalus ventriculorum or internus, when the fluid is confined to the dilated ventricles of the brain; or of—
B. Hydrocephalus meningeus or externus, when the fluid collects between the brain and the dura.
The former condition is much the more common. The cause of hydrocephalus in the young is essentially congenital, and inseparable from imperfect development within the cranium. The forms are occasionally combined. At the time of commencing trouble the skull may be of natural size, but yields to the accumulation of fluid within until it attains relatively enormous dimensions. Most children thus affected die early, some shortly after birth. It is most common in rachitic children. Hydrocephalus developing in the adult is the result almost solely of atrophy of the brain. Pachymeningitis interna (see [p. 572]) may also produce subdural exudate leading to hydrocephalus externus. Encapsulated collections of cerebrospinal fluid due to pachymeningitis interna are known as hygromas of the dura. A ventricular form of hydrocephalus may also result from meningitis and tuberculous disease. The condition is essentially chronic, the fluid collecting in the dilated lateral ventricles, though the third or forth are sometimes also distended: 4000 Cc. of cerebrospinal fluid have been found in more than one instance. As the result of the presence of the fluid there is atrophy of brain, with arrest of development, to such an extent even that the hemispheres are changed into great sacs, being merely spread out upon the outer wall of cystic cavities; all the surface markings are lost, and gray and white substances are scarcely to be differentiated.